performance of the digital llrf systems for cerl …1 performance of the digital llrf systems for...
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Performance of the Digital LLRF Systems for cERL at KEKFeng QIU (KEK) June 10, 2015
ERL2015, Stony Brook, NY USA. June 7-12, 2015
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Main Content
ERL (2015), F. QIU
Introduction
High Level RF system
Low Level RF system
Performance
Disturbances in RF system
Adaptive feedforward control
Summary
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Introduction
ERL (2015), F. QIU
Compact ERL (cERL) is a test facility for the future 3-GeV ERL project. It is a 1.3-GHz superconducting system and is operated in CW mode.
HLRF
Three 2-cell in the Injector
Injector consists of four cavities: Buncher(NC), Injector 1 (SC), Injector 2 (SC), Injector 3 (SC).
Main linac includes two nine-cell cavities (SC).
Layout of cERL
Two 9-cell in ML (SC)
April, 2013, injector commissioning. Oct. 2013, main linac commissioning.
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Main linac
8 kW SSA
Nine-cell SC
16 kW SSA
Main linac Two-cell SC
SC SC
300 kW Kly.
25 kW Kly.
8 kW SSA
Vector-sum Controlling
~8.5 MV/m for main linac Cavities
~3 MV/m for Injector Cavities
~ 20 MeV
Dump
HLRF (Power Source)At present, total four kinds of Power Sources are applied in cERL : 8-kW SSA, 16-
kW SSA, 25-kW Klystron and 300 kW Klystron.
ERL (2015), F. QIU
RF requirement
0.1 % rms, 0.1 deg. rms for cERL0.01% rms, 0.01deg.rms for 3GeV-ERL
4
Cavity QL RF power
Bun. 1.1e5 3 kW
Inj. 1 1.2e6 0.53 kW
Inj. 2 5.8e52.4 kW
Inj. 3 4.8e5
ML1 1.3e7 1.6 kW
ML2 1.0e7 2 kW
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SSA
8 kW SSA
HLRF (Power Distribution System)
ERL (2015), F. QIU
Rather narrow space and complicated waveguide.
Vector-sum controlling for Inj.2 and Inj. 3.
Outside shield
Inside shield
5
100 kW circulator
40 kW circulator6 kW circulator
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ADC: LTC 2208
Xillinx Virtex5 FPGA
ADC & DAC Interface
Digital I/O
uTCA Digital Board
6
LLRF (Digital Board)
Down-convertor
IQ Mod.
FPGA boardsGA bFPGFPGA boards
Thermostatic Chamber(0.01 deg.)
LLRF Cabinet
Digital Board type Feature ADC LTC2208 16 bits, 130 MHz (Max.)DAC AD9783 16 bits, 500 MHz (Max.)FPGA Virtex 5 FX 550 MHz (Max.), includes a Power PC with
Linux, EPICS is installed on the Linux.
LLRF (2013), F. QIU
Four channel 16 bits ADCs + four channel 16 bits DACs.
Xi
Micro TCA
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LLRF (DAQ & communication)LLRF (Tuner + FB) EPICS (Experimental Physics and
Industrial Control System) is installed inside Micro TCA and is used as the DAQ (data acquisition) system.
CSS (Control System Studio) is in charge of the user interface programming.
CSS Interface (FB)
CSS Interface (Tuner)
ERL (2015), F. QIU
Tuner(frequency
ctrl.) FB(field ctrl.)
Piezo
Kly/SSACavity
Pf
Pick up
PfPick up
Pick up
InternetCommunication
PC
FPGA
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MicroTCA
DAC
Digital I/OADC2
ADC1 I/Qdem.
I/QIIR
I/Qdem.
IIRI/Q
detectorsign
Filhold
CW
CCW
Pf
Pick up
Piezo
Mechanical Tuner
KI
KP
8
LLRF (frequency control)
ERL(2015), F. QIU
=
Cavity resonance frequency control: Tuner + Piezo.
Tuner ( TCA)Fine ctrl.
Coarse ctrl.
A&P->I/Q (Unique Mapping)
I
Q
0
0
2 2
0
cos.
sin
.arctan
I AQ A
A I QQ I
Definition
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Calib.ADC
Vector sumI
Q
I_Set
ADCDAC
DAC
cos sinsin cos
FPGA
Power PC
EPICS IOC
IQ M
od.
Waveform Command
Linux
IF 10 MHz
I
AMC Card
AD9783
Dow
n C
onve
rtor
IIR
RF = 1300 MHz
LO 1310 MHzAnalog filter
PI
IIR
Fil.
Q_Set
I_FF
Calib.Q
1300 MHz
Kly. / SSA
Pre. Amp.
Clk 80 MHz
LTC2208ADC
ADC
ADC
PI
Q_FF
cos sinsin cos
DIO (RF SW)SW1
FilFil
bandwidth
Monitor(pick up)
LLRF (field control)
ERL (2015), F. QIU 9
PI ctrl.Epics DAQ
1),1()1()()(: nynxnyIIR
Q
FilFil
FB ( TCA)
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Current Performance (RF field)Amp. Amp.Pha. Pha.
RF stability Bun. Inj. 1 Inj. 2&3 (VS) ML1 ML2
A/A [%. rms] 0.07% 0.006% 0.007% 0.003% 0.003%
[ .rms] 0.04 0.009 0.025 0.010 0.007
40 ms
400 ms
400 ms
400 ms
Beam Momentum jitter is 0.006% (in agreement)
0.006% 0.007% 0.003% 0.003%
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Performance (Beam energy)
11ERL2015 (F. QIU)
Beam momentum jitter is measured by screen monitor and determined by the peak point of the projection of the screen.
Dispersion =2.2m
Resolution62.6 μm/pixel
Screen monitor
Main linac
Injector
~20 MeV
~3.0 MeV
Cam 15
P/P=0.0065%. rms
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R&D (Adaptive FF)
12
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Disturbances in RF system
ERL (2015), F. QIU 13
Main disturbances: High voltage power supply ripples (300 Hz) + burst mode beam-loading (0.5 mA~1mA, 1 ms ~ 2 ms) and Microphonics (DC ~500 Hz ).
1.6 ms500 μA
Cavity
( ) KIPI s KPs
Set
FF s
PS ripples
Microphonics
Beam-loading
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Adaptive FF ctrl
ERL (2015), F. QIU 14
The disturbances estimate can be evaluated accurately if we “know” the mathematical model of the system (disturbance observer).
Disturbance-Observer-Based control (DOB control)
dsGsGdd Pp )()()(ˆ 1
1
P
P
s zG ss ps pG ss z
Model
Cav
PG s
Inv.1
PG s
FFDAC
PS Ripple + Beam
d
d̂
CavFF
DAC
PS Ripple + Beam
d
PG s
Microphonics
Microphonicsd
y
y
Rebuilt
Meas.
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Adaptive FF ctrl (cont’d)
ERL (2015), F. QIU 15
The disturbances estimate can be removed from FF table, thus the disturbance signal d is rejected.
dsGsGdd Pp )()()(ˆ 1
1
P
P
s zG ss ps pG ss z
Model
Cav
PG s
Inv.1
PG s
FFDAC
PS Ripple + Beam
d
d̂
CavFF
DAC
PS Ripple + Beam
d
PG s
Microphonics
Microphonics
removing d̂
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Adaptive FF ctrl (cont’d)
ERL (2015), F. QIU 16
In practical, the combination of AFF control and PI control.
AFF ctrl.PI ctrl.
PI + AFF ctrl.
Cav
PG s
Inv.1
PG s
FF PS Ripple + Beam
d
d̂
Microphonics
Ctrl.
PI(s)Set
Cav
PG s
Inv.1
PG s
FF
PS Ripple + Beam
d
d̂
Microphonics
Cav
PG sFF
PS Ripple + Beam
d
Microphonics
Ctrl.
PI(s)Set
Combination
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Disturbances 1 (HVPS ripples)
ERL (2015), F. QIU 17
Main disturbances: High voltage power supply ripples (300 Hz) + burst mode beam-loading (0.5 mA~1mA, 1 ms ~ 2 ms) and Microphonics (DC ~500 Hz ).
Cavity
( ) KIPI s KPs
Set
FF s
PS ripples
Microphonics
Beam-loading
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Application 1 (HVPS ripples)
ERL (2015), F. QIU 18
Disturbances: high voltage power supply ripples (300 Hz ripples).
PI PI + AFF
Amp. Pha.
FFT
300 Hz
The 300 Hz ripples is disappeared
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Disturbances 2 (beam-loading)
ERL (2015), F. QIU 19
Main disturbances: High voltage power supply ripples (300 Hz) + burst mode beam-loading (0.5 mA~1mA, 1 ms ~ 2 ms) and Microphonics (DC ~500 Hz ).
1.6 ms500 μA
Cavity
( ) KIPI s KPs
Set
FF s
PS ripples
Microphonics
Beam-loading
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Application 2 (Beam-loading)
ERL (2015), F. QIU 20
Disturbances: Beam-loading (about 1.6 ms and 800 μA beam current)
Amp. Pha.
Inj.
1In
j. 2&
3 8 ms
~1.6 ms ~ 800 μA
~ 5 Hz
~1.6 ms ~ 800 μA
~ 5 Hz
Beam profile
Beam-induced
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Disturbances 3 (Microphonics)
ERL (2015), F. QIU 21
Main disturbances: High voltage power supply ripples (300 Hz) + burst mode beam-loading (0.5 mA~1mA, 1 ms ~ 2 ms) and Microphonics (DC ~500 Hz ).
Cavity
( ) KIPI s KPs
Set
FF s
PS ripples
Microphonics
Beam-loading
DC ~ 500Hz
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Application 3 (Microphonics)
ERL (2015), F. QIU 22
Disturbances: Microphonics (DC ~ 500 Hz)
Even with high feedback gains, the microphonics still exist in the measured RF field.
ML1
ML2
50 Hz
50 Hz
The 50 Hz component is disappeared
Microphonics
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Summary
23ERL2015 (F. QIU)
Construction of the RF system for cERL was finished
RF field requirement is satisfied.
Very good beam momentum.
Disturbances in RF system is rejected by a new AFF control
approach
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Back up
24
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DSP algorithms (I/Q detection)
7
0
7
0
)8
2sin(82
)8
2cos(82
ki
ki
kyQ
kyI
I Q
-I -Q
Non
-IQ S
ampl
ing:
IF: Intermediate Frequency Fs: Sampling Frequency
Time [s]
Time [s]
E.g. IF: 10 MHz Fs: 40 MHz
E.g. (cERL) IF: 10 MHz Fs: 80 MHz
IQ S
ampl
ing:
Advantages(non-IQ) • Average effects• Reduce aliasing
=
=
A&P->I/Q (Unique Mapping)
I
Q
0
0
2 2
0
cos.
sin
.arctan
I AQ A
A I QQ I
0
0
2 2
0
cos.
sin
.arctan
I AQ A
A I Q2
Q I
0
0
AA
II 2
Eq. Definition
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Model Based FB optimization
The “Q” filter (LP filter) is used for improving the robustness
(remove the high frequency noises)?
Cav)(sGp
Ctrl)()( 1 sGsQ
p
FF DAC
Klystron Ripple + Beam loading
ADC
u
d
MicroPhonics + Lorentz detuning
d̂
Fil)(sQ
)()()()()()(ˆ 1 sQdsQsQsGsGdd Pp
TipsConnected another system Q(s) with to make sure it can be physically realized.If the Q(s) is an low-pass filter, then the d can be still evaluated.
)(1 sGP
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Total LLRF diagramPI + DOBC (AFF)
Cav)(sGp
Ctrl)()( 1 sGsQ
n
DAC
Q(s)
Delay
Delay
Delay
FL(s)Delay
PI(s)
n
f
uo
d̂
yr
Conj. 4th
Pf
ADC
d
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System IdentificationInput white noise in the DAC output and read the response from the ADC?
Unknown Sys. (RF Sys.)
Step 1: Generate white noise with FPGA
DAC
ADC
FPGA
Step 2: Measured the response of the white noise
A
-A Step 3: Acquire the system model based on the input/output data by system identification method.
white noise
Response
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Application 2 (Beam-loading)
ERL (2015), F. QIU 29
Disturbances: Beam-loading (about 1.6 ms and 800 μA beam current)
Amp. Pha.
Inj.
1In
j. 2&
3 8 ms3ms
(300 Hz)
~1.6 ms ~ 800 μA
~ 5 Hz
~1.6 ms ~ 800 μA
~ 5 Hz
Beam profile
Beam-induced